The present invention relates to a pad spring for use in a tape cassette.
A pad supporting spring for use in a tape cassette is, as well known, formed with a leaf. The pad supporting spring is arranged in the rear of a magnetic tape extended in the cassette along a window hole provided in front of the tape cassette, and serves to press the extended tape, by way of the pad, to the surface of a magnetic head which extends into the cassette from the window hole.
One embodiment of the pad spring previously used will be explained with reference to FIGS. 1 and 2. FIG. 1 is a plan view of a cassette half 2 with a pad spring 1 mounted thereon. The cassette half 2 is a half portion of a tape cassette known as a microcassette (trade name), and provided is with tape hubs 3 and 4 rotatably arranged on both sides thereof, a tape T being wound around the hubs 3,4.
The pad spring 1 is arranged in the rear of the tape T, aligned in the direction of tape feed between the windings. The pad spring 1 is composed of a very thin leaf spring and its surface is arranged in parallel to the tape surface of the feeding tape T. At the center portion 1a of the leaf spring 1 are projecting hemispherical convex portions 1a, 1b providing a (working) fulcrum for the spring toward the inside of the cassette. These convex portions 1a, 1b are made to contact a fulcrum supporting member 7 integrally provided in the cassette half 2.
Both free ends 1e,1f of spring 1 extend in a bifurcated manner from the spring center portion, and pads 8,9 are respectively attached to these free ends. A capstan inserting hole is also provided in cassette half 2.
The pad spring 1 thus constructed presses the pads 8, 9 against the tape when a magnetic head (not shown) is inserted, and the tape is brought into contact with the head surface. Therefore, the tape is suitably brought into contact with the head surface through the pads through an inserting force of the head and a resilient force of the pad spring 1.
However, the magnetic head does not always move horizontally when it enters into the cassette, but as shown in FIG. 3, the magnetic head 14 is sometimes inclined when it enters into the cassette.
In this case, since the center portion having the hemispherical convex portion as the fulcrum of the pad spring, is connected to the pad supporting portion by means of two free ends, the free ends are wider than the center portion. As a result, they are not smoothly brought into contact with each other when contacting to the head and it is impossible to contact the tape with the head under the best condition.
Particularly, in case of using both pads at the same time, a twist of one pad has an influence upon the other pad, so that any rigidity of the free end of the spring is a problem which should be minimized, otherwise good recording and reproduction cannot be carried out.
The construction and the operation of this pad spring are further described in detail in FIGS. 6a-6d.
The pad spring 31, as shown in FIGS. 6a and 6b, is provided at its center with two projections 32a, 32b as its working fulcrum and with pads 34a, 34b attached to free ends 33a, 33b extended from the bent center portion.
The thus constructed pad spring 31, as shown in FIG. 6c, is shifted from the positions (shown by two dots-dash line) of the pad 34b and the free end 33b before being brought into contact with a magnetic head 35, to a portion P' of the head 35 being brought into contact with the pad 34b and to a position P of the head 35 being brought into contact with the pad 34b at a distance X completely entered in the cassette by A. Let a distance from a fulcrum supporting portion 36 made into contact with the convex portion 32b as a working fulcrum of the pad spring 31 to a position P completely made into contact the pad 34b with the head 35 C, and let a distance from the convex 32b to the point P L, the smaller the distances A, C changed by the movement, the better the pad and the head are matched with each other, and as a result, good recording and reproduction can be obtained.
Therefore, it is desired to make a displacement amount at the time of contacting the pad with the head very small in design.